The ultimate objective of the total project is to understand mechanisms involved in the regulation of eukaryotic gene transcription during normal cellular growth and division. Emphasis is being placed on the multiple eukaryotic RNA polymerases, the enzymes responsible for transcription of the nuclear genome. Changes in the RNA polymerase intracellular concentration, endogenous nuclear activity, chemical modification, structural alteration, compartmentalization, the presence of the nuclear (possibly transcriptional) components (poly A polymerase, DNA nicking-closing enzyme, etc.), are being investigated in cells and/or tissues undergoing dramatic changes in the patterns (rates and types) of RNA synthesis. Ultimately it is hoped that correlations between structure or physical dispositions of the multiple enzymes and the modulation of their activities in vivo can be confirmed by in vitro reconstitution experiments using components isolated from tissues undergoing changes in transcriptional activity. Goals set for the current year are to purify and characterize transcriptional components from quiescent and proliferating tissues, to obtain definitive subunit structures of the multiple nuclear RNA polymerases, and to determine if any changes in the structure of these complex enzymes can be observed in tissues representing different physiological states.